Apparatus and Method for Controlling a Gas Stream Temperature or Rate of Temperature Change

ABSTRACT

The invention provides various designs of an apparatus and method for attemperating a gas stream temperature. The apparatus of the present invention provides a body through which a gas stream passes that permits, as desired, a second gas, such as gas outside of the gas duct or such as ambient air, to be added to the main gas stream to attemperate the temperature of the main gas stream. The body or device may be referred to as a variable eductor having a plurality of openings through which a second gas may pass into the main gas stream. The openings may be opened or closed, and the variable eductor provides control over which openings and the degree to which each opening is opened. In some designs the variable eductor is inserted between two portions of a gas duct. The variable eductor has widespread application, such as downstream of a gas turbine to attemperate the exhaust gas temperature during startup.

BACKGROUND OF THE INVENTION Field of the Invention

The invention in its various embodiments relates generally to anapparatus and method for attemperating or controlling the temperature ofa gas stream. In particular, the invention in its various embodimentsrelates to a variable eductor that provides for the addition of a gas toan existing gas stream to attemperate or control the temperature of thegas stream, such as the temperature of an exhaust gas stream from a gasturbine prior to entering a heat recovery stream generator, for example,during startup.

Description of Related Art

In many industrial applications, gas streams have extremely hightemperatures, resulting in thermal stress to infrastructure transportingthese gas streams, including, but not limited to, metal pipes, metalcasings, and the like. For example, during startup of a gas turbine,exhaust gas temperatures exiting the gas turbine into the heat recoverystream generator (HRSG) may climb to almost 1000° F. in less than twominutes. This temperature rise can result in a significant thermalstress event for the HRSG casing and internals. These steam temperatureexcursions during startup have also had a negative impact on the pipingand steam turbine components. Moreover, the demand for flexibleoperation has resulted in combined-cycle units being subjected to anunprecedented number of startup cycles that were not anticipated in theoriginal plant design, thus increasing the number of thermal stressevents for the HRSG.

Therefore, it is desirable to have a means of controlling thetemperature of a gas stream, for example by reducing the temperature ofthe gas stream, as well as controlling the rate of temperature change ofa gas stream. For example, it is desirable to control the temperatureand the rate of temperature increase of an exhaust gas stream from a gasturbine during startup and other transient operations or conditions tominimize thermal stress on the downstream HRSG. It is further desirablethat such means of temperature control be easy to install and easy tooperate, including installation as a retrofit for existing industrialinfrastructure. Therefore, there is a need for an apparatus and methodfor using such an apparatus to control the temperature of a gas stream,for example by reducing the temperature of the gas stream, or to controlthe rate of temperature change of a gas stream the temperature of a gasstream, or both.

BRIEF SUMMARY OF THE INVENTION

Generally, the invention comprises various embodiments of an apparatusand method for controlling the temperature of or attemperating a gasstream, for example by reducing the temperature of the gas stream orcontrolling the rate of temperature change of a gas stream, in which thechange in temperature may be caused by any number of process conditionsor operations, including startup or other transient conditions oroperations. As one of skill in the art will appreciate, there are manyprocesses in which controlling a gas temperature or the rate oftemperature change of a gas stream would be beneficial. Accordingly, theapparatus and method of the present invention has widespreadapplication.

Generally, the apparatus of the present invention provides variousembodiments or designs of a body or device through which a first or maingas stream passes and that permits, as desired, a second gas, such asgas outside of the gas duct or such as ambient air, to be added to themain gas stream to attemperate the temperature of the main gas stream.The body or device, which may be referred to as a variable eductor, isdesigned to pull gas, such as ambient air, from outside of a gas ductcarrying a gas stream into the gas stream. As a result, given atemperature difference between the gas stream in the duct and the secondgas pulled into the duct, the variable eductor can be used to adjust theamount of the second gas pulled into the duct to provide the desiredtemperature control of the gas stream in the duct.

In one embodiment, the present invention provides an apparatus forcontrolling a temperature of a gas stream, comprising a first bodyhaving a first end and a second end and defining a passageway forpassing a gas stream having a temperature from the first end to thesecond end, wherein the body defines at least one opening through whicha second gas from outside of the passageway can pass into thepassageway; and at least one second body attached to the first bodyadjacent to the at least one opening that moves between a first positionand a second position, wherein the at least one second body closes theat least one opening at the first position and opens the at least oneopening at the second position, thereby permitting the second gas topass through the at least one opening into the passageway to change thetemperature of the gas stream.

In some embodiments of the invention, the apparatus has a body having afirst end, a second end, and an outer surface defining a duct orpassageway configured to permit a gas stream to pass through the bodyfrom the first end to the second end. The body has a plurality ofopenings located in the outer surface of the body and a correspondingplurality of shutters, one for each of the openings. Each of theshutters is movably connected to the outer surface such that eachshutter can be opened into the gas duct, thereby creating lower pressureareas behind the shutters within the gas duct and consequently pulling asecond gas, such as a gas from outside of a gas duct, through thecorresponding opening and into the gas duct and the gas stream passingthrough the gas duct. It should be appreciated that each of the shutterscan be operated independently and can be opened to varying degreesthereby providing control over the flow rate of the second gas througheach opening.

In another embodiment, the apparatus has a body that may be a sleevethat connects two ends of two separate gas ducts such that the gasstream passes from the first or upstream gas duct through the sleeve andinto the second or downstream gas duct. In this embodiment, the sleeveis disposed around the outside of a gas duct providing the main gasstream and is sized larger than the outer dimensions this gas duct tocreate a gap or opening between the interior surface of the sleeve andthe outer surface of the gas duct through which a second gas can passinto the main gas stream. The sleeve can slide or be moved back andforth along the gas duct. When moved toward the upstream gas duct, theinterior of the sleeve creates a gas seal with the upstream gas duct,thereby preventing a second gas from passing into the gas duct. Whenmoved in the opposite direction the gas seal is removed therebypermitting the second gas to pass through the opening and into the gasstream.

In another embodiment, the apparatus may be similar to the sleevedescribed above but instead the sleeve rotates about the gas ducts. Inthis case, a plate having a plurality of openings may be attached to theupstream gas duct and disposed at the entrance to the gap or openingcreated between the interior surface of the sleeve and the outer surfaceof the upstream gas duct. A similarly dimensioned plate with a pluralityof openings is attached to the sleeve and positioned adjacent to theplate attached to the outer surface of the upstream gas duct. Theopenings on both plates are positioned such that when the sleeverotates, the plate attached to the sleeve will similarly rotate adjacentto the plate attached to the outer surface of the upstream gas duct.Depending upon the degree of rotation, the corresponding openings onboth plates may partially or completely align such that the openings arepartially or completely open. Accordingly, the sleeve can be rotated topermit a certain amount of the second gas to pass through the openingsbetween the interior surface of the sleeve and the outer surface of theupstream gas duct, through a gap between the sleeve and the outersurface of the upstream gas duct, into the gas stream passing throughthe sleeve, and ultimately into the downstream gas duct.

In another embodiment, the apparatus may also be a sleeve having anattached plate or surface with a plurality of openings positionedradially around the plate as described above in connection with thesleeve that rotates; however, in this embodiment, the sleeve isstationary during use. In this embodiment, shutters, similar to thosedescribed above, are used in connection with the openings in the plateand are controlled in a similar fashion to open, thereby permitting asecond gas to be added to the gas stream passing through the gas duct.Also, similarly, it should be appreciated that each of the shutters canbe operated independently and can be opened to varying degrees therebyproviding control over the flow rate of the second gas through eachopening.

As described above, the apparatus of the invention can be used in amethod to control the temperature of a gas stream or to control the rateof temperature change of a gas stream, either of which has widespreadapplication. For example, in one embodiment, it is desirable to controlthe temperature or the rate of temperature increase, or both, of anexhaust gas stream from a gas turbine during startup and other transientoperations or conditions to minimize thermal stress on a downstream heatrecovery steam generator (HRSG).

In some embodiment, the present invention provides a method forcontrolling a temperature of a gas stream, comprising passing a gasstream having a first gas temperature through a gas duct, wherein aportion of the gas duct comprises a first body having a first end and asecond end and defining a passageway for passing the gas stream from thefirst end to the second end, wherein the body defines at least oneopening, and at least one second body attached to said first bodyadjacent to the at least one opening to open and close the at least oneopening; moving the second body to open the at least one opening,thereby creating a gas pressure lower than a gas pressure of a gasoutside of said passageway, wherein the gas outside of the passagewayhas a second gas temperature different from the first gas temperature,and pulling the gas outside of said passageway into the passageway andinto the gas stream, thereby changing the temperature of the gas stream.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to one embodiment ofthe present invention;

FIG. 2 illustrates the same perspective side view of the apparatus ofFIG. 1 with the shutters in a closed position according to oneembodiment of the present invention;

FIG. 3 illustrates a side view of equipment for operating the shuttersaccording to one embodiment of the present invention;

FIG. 4 illustrates the gas flow through the apparatus of FIG. 1 duringoperation according to one embodiment of the present invention;

FIG. 5 illustrates the gas flow through the apparatus of FIG. 1 duringoperation according to another embodiment of the present invention;

FIG. 6 illustrates the use of the present invention in conjunction witha gas turbine and a heat recovery steam generator (HRSG);

FIG. 7 illustrates simulated performance of the apparatus and method ofthe present invention according to one embodiment of the presentinvention;

FIG. 8 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention;

FIG. 9 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention;

FIG. 10 illustrates a perspective end view of the apparatus forcontrolling a temperature of a gas stream of FIG. 9 according to oneembodiment of the present invention;

FIG. 11 illustrates a perspective side view of the apparatus of FIG. 9in an open position according to one embodiment of the presentinvention;

FIG. 12 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention;

FIG. 13 is a perspective side view of the upstream gas duct and thesleeve of FIG. 12 separated from each other according to one embodimentof the present invention;

FIG. 14 illustrates a perspective side view of the apparatus of FIG. 12in an open position according to another embodiment of the presentinvention;

FIG. 15 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention; and

FIG. 16 illustrates a perspective side view of the apparatus of FIG. 15in an open position according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more fully described below with reference tothe accompanying Figures. While the invention will be described inconjunction with particular embodiments, it should be understood thatthe invention includes alternatives, modifications, and equivalents.Accordingly, the following description is exemplary in that severalembodiments are described (e.g., by use of the terms “preferably,” “forexample,” or “in one embodiment”), but this description should not beviewed as limiting or as setting forth the only embodiments of theinvention, as the invention encompasses other embodiments notspecifically recited in this description. Further, the use of the terms“invention,” “present invention,” “embodiment,” and similar termsthroughout this description are used broadly and are not intended tomean that the invention requires, or is limited to, any particularaspect being described or that such description is the only manner inwhich the invention may be made or used.

Generally, the invention comprises various embodiments of an apparatusand method for controlling the temperature of or attemperating a gasstream, for example by reducing the temperature of the gas stream orcontrolling the rate of temperature change of a gas stream, in which thechange in temperature may be caused by any number of process conditionsor operations, including startup or other transient conditions oroperations. As one of skill in the art will appreciate, there are manyprocesses in which controlling a gas temperature or the rate oftemperature change of a gas stream would be beneficial. Accordingly, theapparatus and method of the present invention has widespreadapplication.

Generally, the apparatus of the present invention provides variousembodiments or designs of a body or device through which a first or maingas stream passes and that permits, as desired, a second gas, such asgas outside of the gas duct or such as ambient air, to be added to themain gas stream to attemperate the temperature of the main gas stream.The body or device, which may be referred to as a variable eductor, isdesigned to pull gas, such as ambient air, from outside of a gas ductcarrying a gas stream into the gas stream. In some embodiments, thevariable eductor is used to create a pressure differential between amain gas stream flowing through a duct and a second gas, such as a gassurrounding the outside of the duct, to effect pulling the second gasinto the gas stream flowing through the duct. In some embodiments, thevariable eductor is used to take advantage of the velocity of the gasstream in the gas duct to pull a second gas, such as a gas surroundingthe outside of the duct, into the gas stream. Accordingly, the variableeductor takes advantage of the velocity and lower pressure of the gasstream passing through the duct. In addition, the variable eductor isdesigned to provide control over the amount of the second gas that ispulled into the duct. As a result, given a temperature differencebetween the gas stream in the duct and the second gas pulled into theduct, the variable eductor can be used to adjust the amount of thesecond gas pulled into the duct to provide the desired temperaturecontrol of the gas stream in the duct. It should be appreciated that theapparatus of the present invention is more than an educator in that italso allows for the control or attemperation of the temperature of thegas stream flowing through the gas duct through the control of theamount of the second gas being pulled into the gas duct and into the gasstream. In some embodiments, this can be accomplished using ambient oratmospheric air as the second gas without the need for complex equipmentand with little to no increase in unit auxiliary load or additionalrequired power requirements. In some embodiments, the variable eductorcan be installed inline in a gas duct or retrofit into an existing gasduct.

It should be appreciated that the variable eductor may be designed invarious ways, some of which are described below, to accomplish the samepurpose of pulling a certain amount of a second gas, such as a gas fromoutside of a gas duct, into the gas duct to control the temperature ofthe gas stream in the gas duct or to control the rate of temperaturechange of the gas stream in gas duct, or both. In some embodiments ofthe invention, the apparatus has a body having a first end, a secondend, and an outer surface defining a duct or passageway configured topermit a gas stream to pass through the body from the first end to thesecond end. The body has a plurality of openings located in the outersurface of the body and a corresponding plurality of shutters, one foreach of the openings. Each of the shutters is movably connected to theouter surface such that each shutter can be opened into the gas duct,thereby creating lower pressure areas behind the shutters within the gasduct and consequently pulling a second gas, such as a gas from outsideof a gas duct, through the corresponding opening and into the gas ductand the gas stream passing through the gas duct. It should beappreciated that each of the shutters can be operated independently andcan be opened to varying degrees thereby providing control over the flowrate of the second gas through each opening. It should be appreciatedthat this ability to independently control each of the shutters allowsfor the asymmetrical introduction of the second gas into the main gasstream, thereby providing control over the distribution or direction offlow of the second gas into the main gas stream and the ability toeffect mixing with the main gas stream and the direction of flow of themain gas stream. For example, controlling which shutters are opened andclosed and to which degree allows for the introduction of the second gasinto the main gas stream to vector the flow of the main gas streamupwards, downwards, or even laterally, with the main gas duct. It shouldalso be appreciated that the orientation and shape of the openings andshutters may be used to control the direction of flow of the second gasinto the main gas stream, thereby effecting mixing and control over thedirection of flow of the main gas stream. Each of the shutters can alsobe closed, thereby preventing the second gas from passing through thecorresponding openings and into the gas duct and gas stream. In thismanner of opening and closing the shutters, the apparatus allows acontrolled amount of the second gas to be added to the gas streampassing through the gas duct. By using a second gas having a differenttemperature, the temperature of the gas stream in the gas duct can becontrolled based upon the flow rate of the second gas. It should beappreciated that in some embodiments, the orientation of the shutters orthe corresponding openings may be designed to provide a certaindirection of gas flow into the gas duct, such as having the second gasflow straight into the gas duct or in a parallel direction to the gasflow of the gas stream in the gas duct or having the gas flow at anangle into the gas duct thus creating a spiral flow of the gas beingpulled into the gas duct.

In another embodiment, the apparatus has a body that may be a sleevethat connects two ends of two separate gas ducts such that the gasstream passes from the first or upstream gas duct through the sleeve andinto the second or downstream gas duct. In this embodiment, the sleeveis disposed around the outside of a gas duct providing the main gasstream and overlaps that gas duct by a given length. In particular, theupstream end of the sleeve is sized larger than the outer dimensions ofthe upstream gas duct to create a gap or opening between the interiorsurface of the sleeve and the outer surface of the upstream gas ductthrough which a second gas can pass into the main gas stream. At theopposite end, the sleeve fits within the downstream gas duct at whichpoint a gas seal is provided between the sleeve and the downstream gasduct. The sleeve can slide or be moved back and forth along thedirection of gas flow or along the length of the upstream or downstreamgas ducts by a given amount. When moved toward the upstream gas duct,the interior of the sleeve creates a gas seal with the upstream gasduct, thereby sealing the gap between the interior surface of the sleeveand the outer surface of the upstream gas duct and preventing a secondgas, such as a gas from passing outside of the gas duct, into the gasduct. This gas seal can be created by an interior funnel portion withinthe sleeve that is attached to the interior surface of the sleeve andthat traverses the opening or gap between the sleeve and the upstreamgas duct and seals against the end of the upstream gas duct or its outersurface near the end of the gas duct. When moved in the oppositedirection along the length of the gas ducts toward the downstream gasduct, the funnel portion of the sleeve is separated from or moved awayfrom the end of the upstream gas duct thereby removing the gas seal andpermitting the second gas to pass through the opening or gap between theinterior surface of the sleeve and the outer surface of the upstream gasduct and into the gas stream passing through the sleeve and ultimatelythe downstream gas duct. In either position, however, a gas seal ismaintained between the sleeve and the downstream gas duct, which may becreated through the use of any means known in the art for creating a gasseal between the sleeve and the downstream gas duct, while allowing thesleeve to move back and forth along the downstream gas duct.

In another embodiment, the apparatus may be similar to the sleevedescribed above but instead of the sleeve moving back and forth alongthe gas ducts, the sleeve rotates about the gas ducts. In this case, aplate or surface having a plurality of openings may be disposed at theentrance to the gap or opening created between the interior surface ofthe sleeve and the outer surface of the upstream gas duct such that ittraverses the gap or opening. This plate may be attached to the outersurface of the upstream gas duct such that it is stationary during use.A similarly dimensioned plate or surface with a plurality of openings isattached to the sleeve and positioned adjacent to the plate attached tothe outer surface of the upstream gas duct such that it also traversesthe gap or opening. The plate may be attached to the sleeve such that itis adjacent either on the inside or outside of plate attached to theouter surface of the upstream gas duct. The openings on both plates arepositioned such that when the sleeve rotates, the plate attached to thesleeve will similarly rotate adjacent to the plate attached to the outersurface of the upstream gas duct. Depending upon the degree of rotation,the corresponding openings on both plates may partially or completelyalign such that the openings are partially or completely open.Correspondingly, the sleeve can be rotated such that the plate attachedto the sleeve partially obstructs or completely blocks the openings onthe plate attached to the outer surface of the upstream gas duct.Accordingly, the sleeve can be rotated to permit a certain amount of thesecond gas to pass through the openings between the interior surface ofthe sleeve and the outer surface of the upstream gas duct, through a gapbetween the sleeve and the outer surface of the upstream gas duct, intothe gas stream passing through the sleeve, and ultimately into thedownstream gas duct. A gas seal is maintained between the sleeve and thedownstream gas duct, which may be created through the use of any meansknown in the art for creating a gas seal between the sleeve and thedownstream gas duct, while allowing the sleeve to rotate.

In another embodiment, the apparatus may also be a sleeve having anattached plate or surface with a plurality of openings positionedradially around the plate as described above in connection with thesleeve that rotates; however, in this embodiment, the sleeve isstationary during use. In this embodiment, shutters, similar to thosedescribed above, are used in connection with the openings in the plateand are controlled in a similar fashion to open, thereby permitting asecond gas to be added to the gas stream passing through the gas duct.Also, similarly, it should be appreciated that each of the shutters canbe operated independently and can be opened to varying degrees therebyproviding control over the flow rate of the second gas through eachopening. Also, as described above, this ability to independently controleach of the shutters allows for the asymmetrical introduction of thesecond gas into the main gas stream, thereby providing control over thedistribution or direction of flow of the second gas into the main gasstream and the ability to effect mixing with the main gas stream and thedirection of flow of the main gas stream. Similarly, the orientation andshape of the openings and the shutters may also be used to effect thedirection of flow of the second gas into the main gas stream.

As described above, the apparatus of the invention can be used in amethod to control the temperature of a gas stream or to control the rateof temperature change of a gas stream, either of which has widespreadapplication. For example, in one embodiment, it is desirable to controlthe temperature or the rate of temperature increase, or both, of anexhaust gas stream from a gas turbine during startup and other transientoperations or conditions to minimize thermal stress on a downstream heatrecovery steam generator (HRSG). During startup of a gas turbine in acombined cycle process, the exhaust gas temperature may climb to almost1000° F. in less than two minutes. This magnitude of temperature risecan result in a significant thermal stress event for the HRSG, includingits casing and internal components and related piping. Similarly,temperature rises may be experienced during transient operations orconditions. In these cases, the apparatus of the present invention maybe used to add a second gas having a lower temperature, such as ambientair, to the exhaust gas from the gas turbine, thereby reducing thetemperature of the exhaust gas and reducing or minimizing the otherwisesignificant temperature rise or spike experienced by the HRSG.Specifically, a user may operate one of the various designs for thevariable eductor to permit a certain amount of a second gas, such as gasfrom outside of the gas duct carrying the gas stream having atemperature to be controlled, to be added to the gas stream. Forexample, a user may open at least one or more of the shutters to allow asecond gas to pass through the corresponding openings in the outersurface of the body of the apparatus of the present invention and intothe gas stream passing concurrently through the apparatus of the presentinvention. Alternatively, a user may move a sleeve that connects two gasduct and that is disposed around the two gas ducts along the directionof gas flow through the gas ducts to allow a second gas to pass throughthe gap between the sleeve and the upstream gas duct and into the gasstream. Alternatively, a user may rotate a sleeve that connects two gasducts and that is disposed around the two gas ducts to partially orcompletely align a plurality of openings in two adjacent plates orsurfaces to allow a second gas to pass through the openings and betweenthe sleeve and the upstream gas duct and into the gas stream.Particularly in the context of a gas turbine, because the gas velocitiesof the exhaust gas through the gas duct are relatively high, and withthe relatively low pressure, educator efficiency would be quite good,thereby relatively easily drawing in ambient atmospheric air toattemperate the exhaust gases entering the HRSG in a controlled fashion.Given the significant temperature difference between the gas turbineexhaust gas temperature and that of the ambient air, relatively smallamounts of ambient air may have a considerable attemperating influence.

It should also be appreciated that in some embodiments, control over arate of temperature increase in a gas stream, due to an upstream processcondition or operation, may also be provided by the apparatus of thepresent invention. For example, again, during startup of a gas turbinein a combined cycle process, the exhaust gas temperature may climb toalmost 1000° F. in less than two minutes. By using the apparatus of thepresent invention, this rate of temperature changed can also becontrolled, as opposed to using the apparatus to achieve a particulartemperature set point. In other words, as the temperature in the gasstream (e.g., the exhaust gas stream from the gas turbine) begins toquickly rise, the apparatus of the invention can be operated to controlthe rate at which that temperature increases, again, as opposed tocontrolling the apparatus to achieve a particular temperature setpoint.In this manner, the effect of a sudden temperature increase ondownstream equipment can be reduced or minimized, regardless of theactual temperature itself.

Following, various embodiments and other features of the apparatus ofthe present invention are described in more detail in connection withthe Figures. Also, the following describes various methods for using theapparatus of the present invention, including, for example, controlmethods for the apparatus.

FIG. 1 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to one embodiment ofthe present invention. As depicted, the apparatus 100 comprises a body101 having a first end 102, a second end 104, and an outer surface 106.The body 101 is roughly cylindrical in shape and is configured to permita gas stream to pass through a gas duct or passageway 108 defined by thebody 101 from the first end 102 to the second end 104. It should beappreciated that the gas stream may be any gas stream whose temperatureor rate of temperature increase is to be controlled, including gasstreams in industrial applications, such as an exhaust gas stream from agas turbine, including a gas turbine whose exhaust gas stream feeds anHRSG.

Additionally, the body 101 comprises a plurality of openings 110distributed along the outer surface 106 of the body 101. The body 101further comprises a plurality of shutters 112 distributed along, andmovably connected to, the outer surface 106. Each of the plurality ofshutters 112 is adjacent to, and associated with, a correspondingopening 110. In the view of the apparatus depicted in FIG. 1, there arethree openings 110 visible. Each opening 110 has a corresponding shutter112 with which it is associated. Additionally, each opening 110, as wellas each shutter 112, is roughly rectangular in shape. It should beappreciated that there may be one or more additional openings 110 andshutters 112 distributed along the outer surface 106 of the body 101that are not visible in the side view depicted in FIG. 1. Thus, itshould be appreciated that there may be any number of openings 110,including five, six, seven, eight, nine, or 10 or more openings 110, andcorresponding shutters 112, distributed along the outer surface 106 ofthe body 101, depending on the exact dimensions of each opening 110 andeach shutter 112. It should be appreciated that depending upon thedegree of attemperation desired by use of the apparatus of the presentinvention, the size and number of the openings 110 can be adjustedappropriately.

It should be appreciated that in some embodiments, the openings 110 aredistributed evenly in a radial direction around the circumference of thebody 101. The openings 110 may also be distributed such that there aretwo circles of opening 110 around the circumference of the body 101. Itshould be appreciated that the openings 110 are defined by edges in theouter surface 106 of the body 101 and that the edges may define anyplanar geometric shape, such as a polygon, including, for example, asquare or rectangle. It should also be appreciated that thecorresponding shutter 112 may have the same geometric circumference asthe corresponding opening 110. Each shutter 112 in some embodiments maybe a flat plate. The body 101 of the apparatus, including each of theplurality of shutters, may be constructed of any suitable material knownto one of skill in the art, including metal or metal alloys.

Each of the plurality of shutters 112 is configured to open relative tothe outer surface 106 of the body 101, thereby permitting a second gas,such as ambient air, to pass from outside of the body 101 through thecorresponding opening 110 and into the gas duct 108. FIG. 1 illustratesthe shutters 112 as being open, which would permit a second gas to passfrom the outside of the body 101 through each corresponding opening 110and into the gas duct 108. Similarly, each of the plurality of shutters112 is configured to close relative to the outer surface 106 of the body101, thereby preventing the second gas from passing from the outside ofthe body 101 through the corresponding opening 112 and into the gas duct108. Accordingly, the plurality of shutters 112 are also configured whenin a closed position to prevent the gas stream within the gas duct 108from leaking or escaping from the gas duct 108.

It should be appreciated that attachment of the shutters 112 to the body101 may be accomplished using any mechanical connector 114 that movablyconnects the shutter 112 to the body 101 and that permits the shutter112 to open and close. In some embodiments, each of the shutters 112 maybe connected using a hinge or hinge-like mechanism. It should beappreciated that one side of the shutter 112 is connected to one of theedges of the outer surface 106 of the body 101 that defines thecorresponding opening 110. As shown in FIG. 1, each of the openings 110are defined by edges in the shape of a polygon, such as a rectangle. Inone embodiment, each of the shutters 112 is attached to a correspondingedge of the opening 112 that is upstream of the other or remaining edgesof the opening 112 relative to the direction of gas flow through the gasduct 108. With respect to FIG. 1, the gas flow through the gas duct 108is from the first end 102 to the second end 104 of the body 101 or fromleft to right. Accordingly, the mechanical connector 114, such as ahinge, is located on the left-most edge of the opening 112. In thiscase, the shutter 112 would rotate about the hinge 114 and when openedwould move inward and into the gas duct 108, thereby protruding into thegas duct 108. In this manner, the shutter 112 creates a low pressurearea on the backside or upstream side of the shutter 112 inside of thegas duct 108, thereby providing a driving force for pulling the secondgas, such as ambient air through the opening 110, such that the secondgas passes over the downstream side of the shutter 112 inside of the gasduct 108 and into the gas duct 108.

FIG. 2 illustrates the same perspective side view of the apparatus ofFIG. 1 with the shutters in a closed position according to oneembodiment of the present invention. As depicted, the shutters 112 aredistributed along the outer surface 106 of the body 101 corresponding toeach opening 110 as shown in FIG. 1. As depicted in FIG. 2, each of thethree visible shutters 112 is closed relative to its correspondingopening 110. It should be appreciated that when any shutter 112 isclosed relative to its corresponding opening 110 it may be substantiallyflush with the outer surface 106. As a result, the gas stream passingthrough the duct 108, as well as the second gas outside of the body 101or adjacent to the outer surface 106, is substantially unable totraverse or pass through a given opening 110.

FIG. 3 illustrates a side view of equipment for operating the shuttersaccording to one embodiment of the present invention. As depicted, ashutter in a closed position 112 a can be attached to the body 101 usingany mechanical connector 114, such as a hinge, that permits the shutterto open and close. The shutter in an open position 112 b results fromthe rotation of one end of the shutter 112 about the axis of a hinge114. The shutter 112 is attached to one end of a linkage 302 that isconnected to an actuator 304 at its other end. The actuator 304 can thenbe controlled by an electrical control signal that causes the actuator304 to move the linkage 302, thereby moving the shutter 112 between aclosed position 112 a and an open position 112 b.

It should be appreciated that the actuator 304 may also be controlled toeffect opening the shutter to any position between those of beingcompletely closed 112 a and completely open 112 b. In this manner, theshutter can be opened to varying amounts or degrees, thereby providing asmaller or larger effective opening through which the second gas maypass into the gas duct 108. Accordingly, opening the shutter to anyposition between fully opened or completely closed provides precisionover the amount of the second gas that is permitted to pass through thecorresponding opening 110 into the gas duct 108, thereby providing morecontrol over the degree of attemperation of the gas stream being fed tothe apparatus of the present invention and into the gas duct 108.Specifically, each of the plurality of varying degrees of opening may beassociated with a specific flow rate of the second gas into the gas duct108. One of skill in the art will appreciate that different flow ratesof the second gas into the gas duct 108 may be determined based, atleast in part, on the dimensions of the opening formed between each ofthe plurality of corresponding openings 110 and each of the plurality ofshutters through which the second gas may pass and the pressure dropacross the opening through which the second gas may pass. Accordingly,the degree to which the shutters are opened can be determined. It shouldbe appreciated that in some embodiments, however, the shutters may onlybe operated to be completely closed or completely opened.

It should be appreciated that one or more control systems may beutilized to adjust the opening and closing of the shutters. In someembodiments, the control system enables simultaneous, ornear-simultaneous, opening and closing of all of the shutters. It shouldalso be appreciated that the control system may be used to open andclose each shutter separately and to control the degree to which eachshutter is separately opened. Accordingly, it should be appreciated thateach of the shutters can be operated independently and can be opened tovarying degrees thereby providing control over the flow rate of thesecond gas through each opening. It should be appreciated that thisability to independently control each of the shutters allows for theasymmetrical introduction of the second gas into the main gas stream,thereby providing control over the distribution or direction of flow ofthe second gas into the main gas stream and the ability to effect mixingwith the main gas stream and the direction of flow of the main gasstream. For example, controlling which shutters are opened and closedand to which degree allows for the introduction of the second gas intothe main gas stream to vector the flow of the main gas stream upwards,downwards, or even laterally, with the main gas duct.

In use, the apparatus of the present invention in its variousembodiments provides the ability to control the temperature of a gasstream that passes through the apparatus or to control the rate of anytemperature change experienced by the gas stream. The apparatus of thepresent invention can be installed in an existing gas duct orincorporated into a new gas duct design in which a user desires toattemperate the temperature of a gas stream that passes though the gasduct. During operation, the gas stream to be attemperated passes throughthe gas duct, including that portion of the gas duct provided by theapparatus of the present invention, such as the gas duct 108 provided bythe body 101 of the embodiment shown in FIG. 1. Upon experiencing a needto attemperate the temperature of the gas stream, such as during startupof a gas turbine or any transient operation where the exhaust gas fromthe gas turbine is the gas stream to be attemperated, at least one ofthe plurality of shutters can be opened to a desired degree of opening,thereby permitting a predefined flow rate of a second gas, such asambient air, to pass through an opening in the body of the apparatus ofthe present invention and into the gas duct. Without being limited bytheory, the apparatus of the present invention provides a variableeductor. Accordingly, the velocity of the gas stream passing through thegas duct acts to pull in the second gas stream from outside of theapparatus' body or outer surface, thereby adding the second gas to thegas stream passing through the gas duct. Therefore, it should beappreciated that the higher the velocity of the gas in the gas duct canaccommodate higher pressures of the second gas outside of the gas duct.Given a temperature difference between the two gas streams and theirrelative mass flow rates, this provides the ability to control thetemperature of the gas stream as its exits the apparatus of the presentinvention of the gas stream or the rate of temperature increase beingexperienced by the gas stream as its exits the apparatus of the presentinvention. Therefore, the apparatus of the present invention is morethan an educator in that it also allows for the control or attemperationof the temperature of the primary gas stream through the controlled useof the plurality of shutters, which can be opened to varying degrees tocontrol the amount of the second gas being pulled into the duct andprimary gas stream and thereby control the temperature of the primarygas stream exiting the apparatus.

The addition of this second gas to the gas stream in the gas duct, basedupon a temperature difference between the second gas stream and the gasstream in the gas duct, results in controlling the temperature of thegas stream in the gas duct or controlling the rate of temperaturechange, such as a rapid increase in temperature, in the gas stream inthe gas duct. In some embodiments, it should be appreciate that thesecond gas may have a lower temperature than that of the first gasstream. Purely as a non-limiting example, in the case of a gas turbine,the second gas may have a temperature that is approximately 1000° F.lower, or more, than the temperature of the gas stream entering thatportion of the gas duct provided by the apparatus of the presentinvention. Accordingly, in one embodiment, the apparatus of the presentinvention may utilize atmospheric air as the second gas to reduce thetemperature of an exhaust gas stream from a gas turbine, particularlyduring startup or during a transient operation or condition in which thetemperature of the exhaust gas stream increases rapidly.

It should be appreciated that the degree to which the shutters may beopen may be adjusted over time depending upon the attemperation requiredfor the gas stream passing through the gas duct. In some embodiments,such adjustments may include fully opening all of the shutters upon aninitial change in the temperature of the gas stream and varying thedegree of opening, such as slowly closing the shutters over time, to apoint where the shutters would be completely closed once the reason forthe temperature change of the gas stream has abated. For example, duringstartup of a gas turbine, the shutters may be fully opened, and as thegas turbine approaches steady-state and the exhaust temperature beginsto stabilized, the shutters may be slowly closed during this perioduntil the point at which the gas turbine and the exhaust gas temperatureare at steady-state, at which time the shutters would be fully closed.In some embodiments, the adjustment of the degree to which the shuttersare opened may be simply fully opening or fully closing a given subsetof shutters.

In certain aspects of the invention, it should be appreciated that therate at which the plurality of shutters can be controlled as well.Purely as a non-limiting example, a user may control the rate of openingof at least one of the plurality of shutters in order to achieve aspecific flow rate of the second gas into the body, thereby achieving adesired reduction in the first gas temperature of the first gas stream.

It should be appreciated that control of the plurality of shutters,including opening and closing, which shutters to open and close, thedegree to which the shutters are opened, and the rate of opening, mayall be controlled. Data may be collected that is used for such controlover the shutters. For example, gas stream temperatures, both upstreamand downstream of the apparatus of the present invention, and thetemperature of the second gas stream (e.g., the ambient air temperature)may be used in a control system, such as a feedback or feedforwardcontrol system, to control the shutters. Other data such as gas streamflow rate and pressure may also be monitored and used to control theshutters. Such monitoring may be achieved by any temperature monitoringdevices including, but not limited to, temperature sensors,thermocouples, and the like.

FIG. 4 illustrates the gas flow through the apparatus of FIG. 1 duringoperation according to one embodiment of the present invention. Asdepicted, the gas stream 402 entering the apparatus 100 of the presentinvention passes into the gas duct 108 provided by the body 101 of theapparatus 100. In this embodiment, the shutters 112 are in an openposition such that a second gas stream 404 passes through the openings110 and is combined with the gas stream 402 entering the gas duct 108.The combined gas streams 406 then exit the gas duct 108 provided by thebody 101 of the apparatus 100.

FIG. 5 illustrates the gas flow through the apparatus of FIG. 1 duringoperation according to another embodiment of the present invention. Asdepicted, the gas stream 402 entering the apparatus 100 of the presentinvention passes into the gas duct 108 provided by the body 101 of theapparatus 100. In this embodiment, the shutters 112 are in a closedposition such that a second gas stream 404 cannot be pulled through thecorresponding openings (not shown as the openings are covered by theclosed shutters 112) or combined with the gas stream 402 entering thegas duct 108. The gas streams 402 then exits the gas duct 108 providedby the body 101 of the apparatus 100 unaffected by the apparatus 100 ofthe present invention.

FIG. 6 illustrates the use of the present invention in conjunction witha gas turbine and a heat recovery steam generator (HRSG). As depicted, agas turbine 602 produces an exhaust gas stream that is passed throughthe apparatus of the present invention 604, such as the embodimentdescribed in connection with FIG. 1. In FIG. 6, three shutters 606 andthree corresponding openings 608 are illustrated, although it should beappreciated that additional shutters and openings may be included in thedesign of the apparatus 604. After passing through the apparatus 604,the gas stream is fed to the HRSG 610. During operation, the exhaust gasstream may have a temperature of up to approximately 1000-1300° F.,which during a cold start may be reached within a few minutes of startupof the gas turbine 602. Accordingly, the shutters 606 would be operatedto allow ambient air to enter the duct through which the exhaust gasstream passes to attemperate the temperature of that gas stream. In someembodiments, the temperature of the exhaust gas stream can be monitoredto allow a control system to modulate the degree of attemperation, forexample, by controlling the number of shutters being opened and thedegree to which they are opened. In this manner, the temperature of theexhaust gas stream, as well as the rate of temperature change, can becontrolled to slowly increase the gas temperature to which the HRSG 610is exposed, particularly during a cold start when a larger degree ofattemperation would be required compared to controlled process operationof the gas turbine and taking into account the materials of constructionof the HRST 610 exposed to the exhaust gas temperature.

FIG. 7 illustrates simulated performance of the apparatus and method ofthe present invention according to one embodiment of the presentinvention. The embodiment illustrated in FIG. 7 is the application ofthe present invention to a gas turbine exhaust gas stream that is fed toan HRSG, as shown, for example, in FIG. 6. Specifically, the embodimentillustrated in FIG. 7 is the application of the present invention to agas turbine exhaust gas stream during a period of time, such as startupor a transient operation, in which the temperature of the exhaust gasstream (“GT Exhaust Temp”) experiences a sudden and significant increasein a short period of time. Accordingly, in this embodiment, theapparatus of the present invention, such as that described above inconnection with FIG. 1, would be part of the duct through which the gasturbine exhaust gas stream passes and be used to attemperate thetemperature of the exhaust gas stream from the gas turbine prior toentering the HRSG.

In response to this sudden increase in temperature of the exhaust gasstream, the shutters on the apparatus of the present invention wouldopen. The specific degree of openness over time is shown in FIG. 7(Shutter Position). As illustrated, the shutters open almostconcurrently with the rate of increase in the gas exhaust temperatureand continue to open more fully as the exhaust gas stream temperaturecontinues to increase. It should be appreciated that in this embodiment,the apparatus and method of the present invention is used to reduce therate of increase of the exhaust gas stream temperature so that the rateof increase of the temperature of that gas stream as it leaves theapparatus of the present invention and enters, for example, an HRSG isreduced. So, although the HRSG will experience an inlet gas stream withan increasing temperature, the rate of increase of that temperature isreduce to be significantly less than the rate of increase of thetemperature of the exhaust gas stream from the gas turbine upstream ofthe apparatus of the present invention. This effect is illustrated inFIG. 7 by the temperature of the gas stream entering the HRSG, which isdownstream of the apparatus of the present invention and after use ofthat apparatus to attemperate the exhaust gas stream from the gasturbine. As shown, the increase of the gas temperature entering the HRSG(HRSG Gas Inlet Temp) does increase but at a much lower rate than thatof the exhaust gas stream exiting the gas turbine. Accordingly, thestress to the HRSG and related components is minimized or reduced byreducing what would otherwise be a sudden and significant increase inthe inlet gas temperature to the HRSG, which can cause significantstress on the HRSG and related components.

It should be appreciated that the designs of the present invention mayalso be used in connection with the process of purging a gas turbinesystem. For example, prior to firing a gas turbine, the gas turbine maybe operated as a fan to purge the system, including the downstreamductwork and the HRSG of any accumulated combustible gases. Thereafter,the gas turbine can be fired and operated. The designs of the presentinvention could be used to increase the mass flow rate of the gasthrough the system during purging, which may result in a reduction inthe amount of time required for purging.

FIG. 8 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention. The apparatus 800 is similar tothat shown in FIG. 1 with the exception of the orientation of theopenings and corresponding shutters. The openings 110 and correspondingshutters 112 in FIG. 1 during use would provide for the second gaspassing through the openings and into the gas stream in the samedirection of gas flow as the gas stream. Specifically, the opening ofthe shutters 112 along the upstream edge of the openings 110 that isessentially normal to the direction of gas flow through the apparatus100 and inward into the gas duct would result in the shutters openingnormal to the direction of gas flow through the apparatus 100.Therefore, the second gas would pass through the openings 110 inessentially the same direction of gas flow as the gas stream in the gasduct or passageway 108. FIG. 8 illustrates a plurality of openings 802that are similar in shape to the openings 110 of FIG. 1 but having edgesdefining the openings 802 that are not parallel to the direction of gasflow 803 through the apparatus 800. In this case, the shutters 804 areattached to an edge of each opening 802 such that upon opening, thesecond gas 806 would pass through the opening 802 and into the gasstream in a direction other than the direction of gas flow of the gasstream 803 in the apparatus 800. In this manner, the second gas wouldcreate a spiral gas flow within the apparatus 800 or passageway withinthe apparatus. The overall impact of this spiral gas flow of the secondgas upon entering the apparatus 800 on the total gas flow and itsdirection would be dependent upon amount of the second gas being addedand its relative velocity/momentum. It should be appreciated thatcontrol over the introduction of the second gas using the orientation ofthe openings and the shutters can be used in conjunction with thecontrol provided by the ability to independently control which shuttersare opened and to what degree as described above.

FIG. 9 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention. As depicted, the apparatus 900 maybe a sleeve 902 that connects two ends of two separate gas ducts 904,906 such that a gas stream 908 (as shown by the arrows) may pass fromthe first or upstream gas duct 904 through a passageway or gas duct 909defined by the sleeve 902 and into the second or downstream gas duct906. In this embodiment, the sleeve 902 is disposed around the outsideof the upstream gas duct 904 and overlaps that gas duct 904 by a givenlength as measured along the direction of gas flow through the gas duct902. In particular, the upstream end 910 of the sleeve 902 is sizedlarger than the outer dimensions of the upstream gas duct 904 to therebydefine or create a gap or opening 912 between the interior surface ofthe sleeve 902 and the outer surface of the upstream gas duct 904. Itshould be appreciated that the size of the gap or opening 912 can bedesigned based upon the sizing of the sleeve 902 about the upstream gasduct 904. The downstream end 911 of the sleeve 902 fits inside of thedownstream gas duct 906, and a circumferential seal can be used toprovide a gas seal between the downstream end 911 of the sleeve 902 andthe downstream gas duct 906. It should be appreciated that impingementof hot gases directly upon the circumferential seal can be minimized orprevented by virtue of the sleeve 902 fitting inside of the downstreamgas duct 906, which in turn reduces the potential for seal failure andgas leakage. In one embodiment, the circumferential seal between theinterior surface of the downstream gas duct 906 and the exterior surfaceof the sleeve 902 is a high temperature flexible metallic gasket affixedaround the entire exterior circumference of the sleeve 902 at or nearthe downstream end of the sleeve 902.

The sleeve 902 can slide back and forth along the direction of gas flow(as shown by the direction of the arrows representing the gas stream908) or along the length of the gas ducts 904, 906 by a given amount.The movement of the sleeve 902 can be controlled using an actuator motor913. When moved along the lengths of the gas ducts 904, 906 toward theupstream gas duct 904, the interior of the sleeve 902 creates a gas sealwith the upstream gas duct 904 or seals against the surface of theupstream gas duct 904, thereby sealing the gap or opening 912 betweenthe interior surface of the sleeve 902 and the outer surface of theupstream gas duct 904 and preventing a second gas, such as a gas frompassing outside of the sleeve 902 or upstream gas duct 904 into thesleeve 902. This gas seal can be created by an interior funnel portionor collar 914 attached within the sleeve 902, such as to an insidesurface of the sleeve 902, that traverses the gap or opening 912 andengages or seals against the end of the upstream gas duct 904 or itsouter surface near the end of the gas duct 904 when the sleeve 902 ismoved toward the upstream gas duct 904. Accordingly, as shown in FIG. 9,the apparatus 900 is illustrated in a closed position such that a gasseal has been created between the interior surface of the sleeve 902 andthe outer surface of the upstream gas duct 904, which prevents gas frompassing through the gap or opening 912 in either direction. It should beappreciated that the circumferential gas seal between the downstream end911 of the sleeve 902 and the downstream gas duct 906 is maintainedduring use of the sleeve 902, including its sliding back and forth.Accordingly, the connection between the downstream end 911 of the sleeve902 and the downstream gas duct 906 must provide for the ability for thesleeve 902 to move back and forth along the downstream gas duct 906while maintaining the gas seal. The gas seal is maintained at thislocation to avoid the release of any gas from the gas stream at thispoint.

FIG. 10 illustrates a perspective end view of an apparatus forcontrolling a temperature of a gas stream of FIG. 9 according to oneembodiment of the present invention. As depicted, the sleeve 902 has afunnel portion or collar 914 that is positioned within the sleeve 902.The collar 914 is attached to the inside surface of the sleeve 902 andis angled or tapered away from that surface and inwardly toward thecenter of the sleeve 902. The terminal edge 1002 of the funnel portionor collar 914 mates with the outer surface of the upstream gas duct 904to create a gas seal that prevents gas from passing through the gap 912between the interior surface of the sleeve 902 and the outer surface ofthe upstream gas duct 904. It should be appreciated that the gas sealdoes not preclude the sleeve 902 from moving back and forth. In oneembodiment, the terminal edge 1002 of the funnel portion or collar 914may contain a flexible portion, such as a rubber gasket or similar part,that when engaged against the upstream gas duct, creates the gas seal atthe edge of the upstream gas duct 904. It should be appreciated thatother designs may be used to create the gas seal between the interiorsurface of the sleeve 902 and the outer surface of the upstream gas duct904.

FIG. 11 illustrates a perspective side view of the apparatus of FIG. 9in an open position according to one embodiment of the presentinvention. As depicted, the sleeve 902 has been moved toward thedownstream gas duct 906, thereby removing the gas seal between theupstream gas duct 904 and the funnel portion or collar 914 of the sleeve902. Accordingly, the sleeve 902 is shown in an open position as thefunnel or collar 914 is positioned away from or separated from the endof the upstream gas duct 904. In this case, the gas stream 908 simplypasses through the opening 1102 of the funnel portion or collar 914. Asthe gas stream 908 passes through the passageway or duct 909 within thesleeve 902, the second gas 1104, such as gas located outside of theupstream gas duct 904 or ambient air, is pulled through the gap oropening 912 and into the gas stream 908 within the passageway within thesleeve 902. Based upon a temperature difference between the second gasstream 1102 and the gas stream 908 in the gas duct, the addition of thissecond gas 1102 to the gas stream 908 in the gas duct results incontrolling the temperature of the gas stream 908 in the gas duct orcontrolling the rate of temperature change, such as a rapid increase intemperature, in the gas stream 908 in the gas duct. It should beappreciated that the sleeve 902 may be moved to any position between afully open position and the closed position shown in FIG. 9. Positioningthe sleeve 902 at a position between fully open and closed provides theability to control the amount of gas flowing through the gap 912 due tothe relative position of the funnel portion or collar 914 and the end ofthe upstream gas duct 904. In other words, as the collar 914 is movedcloser to the end of the gas duct 904, the gap 912 will become morerestricted thus permitting less gas to pass from outside of the upstreamgas duct 904 through the gap 912 and into the gas stream 908 in thesleeve 902.

Again, it should be appreciated that regardless of the position of thesleeve 902, the circumferential gas seal with the downstream gas duct906 is maintained. It should be appreciated that any means known in theart for creating a gas seal between the sleeve 902 and the downstreamgas duct 906, while allowing the sleeve 902 to move back and forth alongthe downstream gas duct 906 may be used.

FIG. 12 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention. As depicted, the apparatus 1200 maybe a sleeve 1202 that connects two ends of two separate gas ducts 1204,1206 such that a gas stream 1208 (as shown by the arrows) may pass fromthe first or upstream gas duct 1204 through a passageway or gas duct1209 defined by the sleeve 1202 and into the second or downstream gasduct 1206. In this embodiment, the sleeve 1202 is disposed around theoutside of the upstream gas duct 1204 and overlaps that gas duct 1204 bya given length as measured along the direction of gas flow through thegas duct 1202. In particular, the upstream end 1210 of the sleeve 1202is sized larger than the outer dimensions of the upstream gas duct 1204to define or create a gap or opening 1212 between the interior surfaceof the sleeve 1202 and the outer surface of the upstream gas duct 1204.The downstream end 1211 of the sleeve 1202 fits inside of the downstreamgas duct 1206, and a circumferential seal can be used to provide a gasseal between the downstream end 1211 of the sleeve 1202 and thedownstream gas duct 1206. It should be appreciated that impingement ofhot gases directly upon the circumferential seal can be minimized orprevented by virtue of the sleeve 1202 fitting inside of the downstreamgas duct 1206, which in turn reduces the potential for seal failure andgas leakage. In one embodiment, the circumferential seal between theinterior surface of the downstream gas duct 1206 and the exteriorsurface of the sleeve 1202 is a high temperature flexible metallicgasket affixed around the entire exterior circumference of the sleeve1202 at or near the downstream end of the sleeve 1202.

At the upstream end 1210 of the sleeve 1202, a plate 1214 having aplurality of openings or holes or ports 1216 is attached to the upstreamend 1210 of the sleeve 1202 and extends from the sleeve 1202 inwardlytoward the surface of the upstream gas duct 1204. The plate 1214 can bemade from the same materials of construction as the sleeve 1202, and theopenings 1216 can be any shape or size and there can be any desirednumber of openings 1216. As described below, a second gas to be added tothe gas stream 1208 will pass through these openings 1216. Accordingly,in designing the openings 1216, including the cross-sectional area ofeach opening 1216 and the overall total cross-sectional area availablefor the second gas to pass through should be taken into account.

A similarly designed plate 1218 is attached to the outer surface of theupstream gas duct 1204 and has a set of openings or holes or ports 1220that corresponds in size, shape, and number to the openings 1216 in theplate 1214 attached to the sleeve 1202. It should be appreciated thatthe plate 1218 attached to the outer surface of the upstream gas duct1204 is attached such that it is stationary. The plate 1218 attached tothe outer surface of the upstream gas duct 1204 extends outwardly suchthat it is parallel to the plate 1214 attached to the sleeve 1202.Further, the plate 1218 attached to the outer surface of the upstreamgas duct 1204 is positioned along the upstream gas duct 1204 such thatit is adjacent to the plate 1214 attached to the sleeve 1202. It shouldbe appreciated that the plate 1218 attached to the outer surface of theupstream gas duct 1204 positioned such that it is on either side of theplate 1214 attached to the sleeve 1202.

As shown in FIG. 12, the openings 1216 in the plate 1214 attached to thesleeve 1202 are offset or misaligned relative to the openings 1220 inthe plate 1218 attached to the outer surface of the upstream gas duct1204. Accordingly, a second gas cannot pass through either set ofopenings 1216, 1220 in either plate 1214, 1218, effectively creating agas seal and preventing gas from passing into or out of the gap 1212. Inthis position, the sleeve 1202 is in a closed position, and no secondgas can be added to the gas stream 1208 passing through the sleeve 1202.It should be appreciated that when the openings are offset, adequatesealing of the openings can be accomplished by a similar hightemperature metallic gasket material affixed around the circumference ofeach opening on the posterior surface to seal against the anteriorsurface.

In this embodiment, the sleeve 1202 can rotate around an axis defined bythe longitudinal center of the passageway or gas duct 1209 created bythe sleeve 1202. As depicted, the sleeve 1202 can rotate in bothdirections as shown by the arrow 1222 shown in FIG. 12. It should beappreciated that the sleeve 1202 can rotate to any position around thisaxis. The rotation of the sleeve 1202 can be controlled using anactuator motor (not shown). When rotated, the openings 1216 in the plate1214 attached to the sleeve 1202 can be aligned with the openings 1220in the plate 1218 attached to the outer surface of the upstream gas duct1204. Accordingly, a second gas from outside of the upstream gas duct1204 can then pass through the openings 1216, 1220 in both plates 1214,1218, through the gap 1212, and into the gas stream 208 passing throughthe passageway provided by the sleeve 1202. It should be appreciatedthat since the sleeve 1202 can rotate to any position around its axis ofrotation that the openings 1216, 1220 in both plates 1214, 1218 can bealigned such that the openings 1216, 1220 are completely open orpartially open. For example, the sleeve 1202 can be rotated such thatthe openings 1216 in the plate 1214 attached to the sleeve 1202partially obstruct the corresponding openings 1218 in the sleeveattached to the upstream gas duct 1204.

FIG. 13 is a perspective side view of the upstream gas duct and thesleeve of FIG. 12 separated from each other according to one embodimentof the present invention. As shown, the sleeve 1202 has a plate 1214attached to either the end of the sleeve 1202 or to its interior surfacenear the end of the sleeve 1202. This plate 1214 is generally a flatplate that traverses the perimeter of the sleeve 1202. In thisembodiment, the sleeve 1202 is a circular tube such that the plate 1214is also circular. The plate 1214 has the plurality of openings 1216.

Also as shown, the upstream gas duct 1204 has a plate 1218 that issimilarly shaped and sized to the plate 1214 attached to the sleeve1202. The plate 1218 attached to the upstream gas duct 1204 has asimilarly number of openings 1220 that are similarly sized to theopenings 1216 in the plate 1214 attached to the sleeve 1202. The plate1218 is positioned a given length from the end of the upstream gas duct1204 such that when the sleeve 1202 is positioned over this end of theupstream gas duct 1204, a portion of the upstream gas duct will extendwithin the sleeve 1202 to the point that the plate 1218 is adjacent tothe plate 1214 attached to the sleeve 1202. As described, as the sleeve1202 is rotated, the degree of rotation can be used to determine theextent to which the openings 1216, 1220 in both plates 1214, 1218 arealigned.

FIG. 14 illustrates a perspective side view of the apparatus of FIG. 12in an open position according to another embodiment of the presentinvention. As depicted, the sleeve 1202 has been rotated such that theopenings 1216, 1220 in both plates 1214, 1218 are aligned and permit thefull flow of a second gas 1402 to pass from outside of the upstream gasduct 1204, through the openings 1216, 1220 in both plates 1214, 1218,through the gap 1212 between the interior surface of the sleeve 1202 andthat portion of the outer surface of the upstream gas duct 1204 withinthe sleeve 1202, and into the gas stream 1208 passing through thepassageway 1209 provided by the sleeve 1202.

Based upon a temperature difference between the second gas stream 1402and the gas stream 1208 in the gas duct, the addition of this second gas1402 to the gas stream 1208 in the gas duct results in controlling thetemperature of the gas stream 1208 in the gas duct or controlling therate of temperature change, such as a rapid increase in temperature, inthe gas stream 1208 in the gas duct. It should be appreciated that thesleeve 1202 may be rotated to any position between a fully open positionat which the openings 1216, 1220 in both plates 1214, 1218 are fullyaligned and completely open as shown in FIG. 14 and the closed positionat which the openings 1216, 1220 in both plates 1214, 1218 are offset ornot aligned and prevent the passing of any gas through the correspondingplates 1214, 1218 and into the gas stream 1208 within the passageway1209 of the sleeve 1202 as shown in FIG. 12. Positioning the sleeve 1202at a position between fully open and closed provides the ability tocontrol the amount of gas flowing through the gap 1212. In other words,as the openings 1216, 1220 become more aligned more gas can pass fromoutside of the upstream gas duct 1204 through the gap 1212 and into thegas stream 1208 in the sleeve 1202.

It should be appreciated that the circumferential gas seal between thedownstream end 1211 of the sleeve 1202 and the downstream gas duct 1206is maintained during use of the sleeve 1202, including during itsrotation to any position. Accordingly, the connection between thedownstream end 1211 of the sleeve 1202 and the downstream gas duct 1206must provide for the ability for the sleeve 1202 to rotate whilemaintaining the gas seal. The gas seal is maintained at this location toavoid the release of any gas from the gas stream at this point.

It should be appreciated that the various designs of the apparatus ofthe present invention as shown in FIGS. 9-14 may also be used asdescribed and shown in connection with FIGS. 4-6. Although the apparatusof FIG. 1 was referred to regarding FIG. 4-6, the apparatus of FIG. 1could be replaced with the apparatuses of FIGS. 9-14, noting thatreferences to operating the shutters of the apparatus of FIG. 1 wouldinstead refer to operation of the sleeves of FIGS. 9-14, includingsliding the sleeve or rotating the sleeve as applicable.

FIG. 15 illustrates a perspective side view of an apparatus forcontrolling a temperature of a gas stream according to anotherembodiment of the present invention. The embodiment depicted in FIG. 15is a sleeve similar to those described in connection with FIGS. 9 and 12with the exception that in this embodiment the sleeve is stationary.This embodiment is also similar to the sleeve described in connectionwith FIG. 12 in that a plate having a plurality of openings is attachedto the inside surface of the sleeve and traverse the gap or openingbetween the sleeve and the outer surface of the upstream gas duct.However, in this embodiment, a corresponding plurality of shutters areattached to plate and control the passage of a second gas from outsideof the gas duct into the sleeve and the main gas stream.

As depicted, the apparatus is a sleeve 1502 that connects two ends oftwo separate gas ducts 1504, 1506 such that a gas stream 1514 (as shownby the arrows) may pass from the first or upstream gas duct 1504 througha passageway or gas duct defined by the sleeve 1502 and into the secondor downstream gas duct 1506. In this embodiment, the sleeve 1502 isdisposed around the outside of the upstream gas duct 1504 and overlapsthat gas duct 1504 by a given length as measured along the direction ofgas flow 1514 through the gas duct 1502. In particular, the upstream endof the sleeve 1502 is sized larger than the outer dimensions of theupstream gas duct 1504 to thereby define or create a gap or opening 1512between the interior surface of the sleeve 1502 and the outer surface ofthe upstream gas duct 1504. It should be appreciated that the size ofthe gap or opening 1512 can be designed based upon the sizing of thesleeve 1502 about the upstream gas duct 1504. The downstream end of thesleeve 1502 fits inside of the downstream gas duct 1506, and acircumferential seal can be used to provide a gas seal between thedownstream end of the sleeve 1502 and the downstream gas duct 1506. Itshould be appreciated that impingement of hot gases directly upon thecircumferential seal can be minimized or prevented by virtue of thesleeve 1502 fitting inside of the downstream gas duct 1506, which inturn reduces the potential for seal failure and gas leakage. In oneembodiment, the circumferential seal between the interior surface of thedownstream gas duct 1506 and the exterior surface of the sleeve 1502 isa high temperature flexible metallic gasket affixed around the entireexterior circumference of the sleeve 1502 at or near the downstream endof the sleeve 1502.

At the upstream end of the sleeve 1502, a plate 1508 is attached to theupstream end of the sleeve 1502 and extends from the sleeve 1502inwardly toward the surface of the upstream gas duct 1504. The plate hasa plurality of shutters 1510 that cover a corresponding plurality ofopenings or holes or ports. The shutters 1510 may be designed andoperated as described above in connection with FIGS. 1-5 and 8,including the ability to independently control each shutter 1510. Asshown, the shutters 1510 are currently in a closed position in that theyare covering the corresponding plurality of openings and preventing thepassage of gas from outside of the gas duct 1504, such as ambient air,into the sleeve 1502 and the gas stream 1514.

FIG. 16 illustrates a perspective side view of the apparatus of FIG. 15in an open position according to another embodiment of the presentinvention. As depicted, the shutters 1510 are shown in an open positionsuch that the corresponding openings 1602 are visible. In this position,a second gas 1604 can pass through the gap or opening 1512, through theopenings 1602 in the plate 1508, and into the main gas stream 1514.

Various embodiments of the invention have been described above. However,it should be appreciated that alternative embodiments are possible andthat the invention is not limited to the specific embodiments describedabove. For examples, while the invention has been described in thecontext of a gas turbine and attemperation of the exhaust gas streamfrom the gas turbine prior to entering a HRSG, the invention may be usedin other industrial gas streams where it is desirable to either controla gas stream temperature or reduce a rate of increase of a gas streamtemperature. It should be appreciated that, in at least some of theembodiments of the invention, such as the embodiment depicted in FIG. 1,the apparatus does not comprise, and need not comprise, any fans,sprays, dampers, bypass systems, or similar structures. Therefore, theapparatus permits temperature control of a gas stream, including anexhaust gas stream from a combustion turbine, in a relativelystraightforward manner, without the need to install complex andpotentially expensive auxiliary cooling systems, such as fan systems. Itshould further be appreciated that the apparatus is capable ofattachment directly to a metal pipe through which a gas stream flows,including, but not limited to, a gas exhaust pipe of a combustionturbine. Attachment may be achieved through mechanisms familiar to oneof skill in the art, including, but not limited to, screws, nuts, bolts,and the like. Therefore, the apparatus is compatible with existingindustrial structures, including pipe structures and pipe networks,without the need for specialized attachment mechanisms.

What is claimed is:
 1. An apparatus for controlling a temperature of agas stream, comprising: a first body having a first end and a second endand defining a passageway for passing a gas stream having a temperaturefrom said first end to said second end, wherein said body defines atleast one opening through which a second gas from outside of saidpassageway can pass into said passageway; and at least one second bodyattached to said first body adjacent to said at least one opening thatmoves between a first position and a second position, wherein said atleast one second body closes said at least one opening at said firstposition and opens said at least one opening at said second position,thereby permitting the second gas to pass through said at least oneopening into said passageway to change the temperature of the gasstream.
 2. The apparatus of claim 1, wherein said first body comprisesan outer surface defining the passageway, wherein said at least oneopening comprises a plurality of openings in said outer surface, whereinsaid at least one second body comprises a plurality of shutters eachmovably connected to said outer surface and adjacent to a correspondingone of said openings, and wherein each of said shutters opens inwardlyinto the passageway.
 3. The apparatus of claim 2, wherein each of saidplurality of shutters is configured to independently move to a pluralityof positions between said first position and said second position, andwherein each of said plurality of positions has a corresponding flowrate of the second gas through each of said corresponding openings. 4.The apparatus of claim 3, further comprising: at least one controlmechanism configured to open at least one of said plurality of shuttersto at least one of said plurality of positions and configured to closesaid at least one of said plurality of shutters.
 5. The apparatus ofclaim 1, wherein said first body is configured to attach to a first gasduct at said first end and to a second gas duct at said second end topass the gas stream from the first gas duct through said passageway tothe second gas duct.
 6. The apparatus of claim 1, further comprising: agas turbine having an exhaust gas outlet duct that is fluidly connectedto said first body at said first end; and a heat recovery steamgenerator that is fluidly connected to said first body at said secondend.
 7. The apparatus of claim 1, wherein said first end is configuredto receive an end of a gas duct providing the gas stream; wherein saidat least one opening is defined between said first body and the gasduct; wherein said first body is configured to slide between a firstposition and a second position; wherein said second body comprises acollar attached to an inside surface of said first body that traversessaid at least one opening and seals against an outer surface of the gasduct when said first body is in said first position, thereby closingsaid at least one opening, and that is separated from the outer surfaceof the gas duct when said first body is in a second position, therebypermitting the second gas to pass through said at least one opening intosaid passageway.
 8. The apparatus of claim 8, wherein said first body isconfigured to slide between a plurality of positions between said firstposition and said second position, thereby partially opening said atleast one opening.
 9. The apparatus of claim 8, wherein said first bodycomprises a cylindrical shape.
 10. The apparatus of claim 8, furthercomprising: a gas turbine having an exhaust gas outlet, wherein the gasduct is fluidly connected to said exhaust gas outlet; and a heatrecovery steam generator having a gas stream inlet that is fluidlyconnected to said first body at said second end.
 11. The apparatus ofclaim 1, wherein said first end of said first body is configured toreceive an end of a gas duct providing the gas stream; wherein said atleast one opening is defined between said first body and the gas duct;wherein said second body comprises a first collar attached to an insidesurface of said first body that traverses said at least one opening andthat defines a plurality of openings; wherein the gas duct comprises asecond collar disposed on its outer surface adjacent to said firstcollar that defines a second plurality of openings, each one of saidsecond plurality of openings corresponding to one of said firstplurality of openings; and wherein said first body is configured torotate between a first position at which said first plurality ofopenings is offset from said second plurality of openings and a secondposition at which said first plurality of openings is at least partiallyaligned with said second plurality of openings thereby permitting thesecond gas to pass through said at least one opening into saidpassageway.
 12. The apparatus of claim 12, wherein said body isconfigured to rotate to a plurality of positions.
 13. The apparatus ofclaim 1, wherein said first end of said first body is configured toreceive an end of a gas duct providing the gas stream; wherein said atleast one opening is defined between said first body and the gas duct;wherein said second body comprises a collar attached to an insidesurface of said first body that traverses said at least one opening andthat defines a plurality of openings and a plurality of shutters eachmovably connected to said collar and adjacent to a corresponding one ofsaid openings, and wherein each of said shutters opens inwardly towardsaid passageway.
 14. An apparatus for controlling a temperature of a gasstream, comprising: a first body having a first end and a second end anddefining a passageway for passing a gas stream having a temperature fromsaid first end to said second end, wherein said body defines at leastone opening through which a second gas from outside of said passagewaycan pass into said passageway; and at least one second body attached tosaid first body adjacent to said at least one opening that moves betweena first position and a second position, wherein said at least one secondbody closes said at least one opening at said first position and openssaid at least one opening at said second position, thereby permittingthe second gas to pass through said at least one opening into saidpassageway to change the temperature of the gas stream; and at least onecontrol mechanism configured to move said at least one second bodybetween said first position and said second position.
 15. The apparatusof claim 15, further comprising: a gas turbine having an exhaust gasoutlet duct that is fluidly connected to said first end of said firstbody; and a heat recovery steam generator that is fluidly connected tosaid second end of said first body.
 16. A method for controlling atemperature of a gas stream, comprising: passing a gas stream having afirst gas temperature through a gas duct, wherein a portion of the gasduct comprises a first body having a first end and a second end anddefining a passageway for passing the gas stream from said first end tosaid second end, wherein said body defines at least one opening, and atleast one second body attached to said first body adjacent to said atleast one opening to open and close said at least one opening; movingsaid second body to open said at least one opening, thereby creating agas pressure lower than a gas pressure of a gas outside of saidpassageway, wherein said gas outside of said passageway has a second gastemperature different from said first gas temperature, and pulling thegas outside of said passageway into said passageway and into the gasstream, thereby changing the temperature of the gas stream.
 17. Themethod of claim 17, further comprising: monitoring the first gastemperature of the gas stream; and controlling a degree of opening of atleast one of the plurality of openings in response to said monitoring.18. The method of claim 17, wherein said gas duct comprises a inlet endand an outlet end, wherein said passing comprises passing the gas streamfrom a gas turbine to said inlet end of said gas duct and through saidduct to said outlet end, and further comprising: passing the gas streamfrom said outlet end to a heat recovery stream generator.
 19. The methodof claim 19, wherein said passing the gas stream from the gas turbine isperformed during a startup of the gas turbine.